i 9 i2] CURRENT LITERATURE 443 



The tenth and last chapter deals with heredity and sex. The hypothesis 

 offered by the author several years ago that the female regularly possesses a 

 chromatic element, or something else in addition to the possessions of the male, 

 is made the key to the entire discussion of this subject, and a series of facts is 

 presented which give the hypothesis considerable apparent plausibility, 

 although the philosophical basis for it seems to the reviewer to be a little 

 strained. This basis is found in the statement that the female as compared 

 with the male has an additional function, namely the supplying of nourishment 

 to the young zygote. On the other hand, it may be pointed out that the male 

 differs from the female in many functions, and is in many respects morpho- 

 logically and physiologically the superior sex, and it is possible to interpret 

 these differences as additions to the female. If the egg has the added function 

 of nourishing the young zygote, the sperm has the added function of motility, 

 and there seems no better a priori ground for expecting an additional chromatin 

 element to represent one of these additions than the other. The reviewer 

 believes that there is no sufficient ground at present for the assumption that 

 sex is always determined in the same manner. It' cannot be determined as yet 

 whether the basic differences between the sexes are quantitative or qualitative, 

 and in either case the same results might be attained by any one of several 

 different methods. The attempt to bring the sex-phenomena of all organisms 

 under a single viewpoint is premature. 



Each of the chapters is followed by a "bibliography," but the meagerness 

 of the literature lists may be judged from the fact that they include only 

 46 titles from 26 authors, including 14 of CASTLE'S own papers. This may 

 be compared with the bibliography appended to another recent book on 

 heredity which includes 426 titles from 170 authors. However, this is not 

 intended as an adverse criticism of CASTLE'S excellent book, but is mentioned 

 to show the limitations of its author's aims. Extensive literature lists are 

 indispensable to students, but would defeat their own purpose in a book 

 intended primarily for popular reading. 



The press work is excellent and typographical errors are few, though 

 "reversion" is rendered "revision" in the heading of chap. iv. GEORGE H. 

 SHULL. 



